Add maintenance commands to README

Co-authored-by: Frederico Sabino <3332770+fmrsabino@users.noreply.github.com>

README.md

@@ -142,11 +142,27 @@ docker exec -it safe-transaction-service-web-1 python manage.py createsuperuser
 - [v1.3.0 L2](https://github.com/safe-global/safe-deployments/blob/main/src/assets/v1.3.0/gnosis_safe_l2.json)
 - [Other related contracts and previous Safe versions](https://github.com/safe-global/safe-deployments/blob/main/src/assets)
 
-## Troubleshooting
+## Service maintenance
 
-### Issues installing grpc on a Mac M1
+Service can run into some issues when running in production:
 
-If you face issues installing the `grpc` dependency locally (required by this project) on a M1 chip, set `GRPC_PYTHON_BUILD_SYSTEM_OPENSSL=1` and `GRPC_PYTHON_BUILD_SYSTEM_ZLIB=1` and then try to install the dependency again.
+### Indexing issues
+You can tell there are indexing issues if:
+- Executed transactions are missing from the API (`all-transactions`, `multisig-transactions`, `module-transactions`... endpoints). If you use the [Safe{Wallet} Web client](https://github.com/safe-global/safe-wallet-web) you should check what is the current state of the Safe Client Gateway cache as it might have outdated data.
+- Asset transfers (ERC20/721) are missing from `all-transactions` or `transfers` endpoints.
+- You see error logs such as "Cannot remove owner" or similar inconsistent errors when `worker-indexer` is processing decoded data.
+
+There are multiple options for this. Connect to either `web` or `worker` instances. Running commands inside of `tmux` is recommended
+(installed by default):
+- `python manage.py check_index_problems`: it will try to automatically fix missing transactions.
+Tokens related transactions (ERC20/721) will not be fixed with this method. This method will take a while, as it needs to compare
+database data with blockchain data for every Safe.
+- `python manage.py reindex_master_copies --from-block-number X --addresses 0x111 0x222`: if you know the first problematic block,
+it's faster if you trigger a manual reindex. `--addresses` argument is optional, but if you know the problematic Safes providing
+them will make reindexing **way** faster, as only those Safes will be reindexed (instead of the entire collection).
+
+If you see ERC20/ERC721 transfers missing:
+- `python manage.py reindex_erc20 --from-block-number X --addresses 0x111 0x222`: same logic as with `reindex_master_copies`.
 
 ## FAQ
 ### Why `/v1/safes/{address}` endpoint shows a nonce that indicates that a transaction was executed but the transaction is not shown or marked as executed in the other endpoints?
@@ -176,5 +192,11 @@ https://docs.safe.global/learn/safe-core/safe-core-api/available-services
 ### What means banned field in SafeContract model?
 The `banned` field in the `SafeContract` model is used to prevent indexing of certain Safes that have an unsupported `MasterCopy` or unverified proxies that have issues during indexing. This field does not remove the banned Safe and indexing can be resumed once the issue has been resolved.
 
+## Troubleshooting
+
+### Issues installing grpc on a Mac M1
+
+If you face issues installing the `grpc` dependency locally (required by this project) on a M1 chip, set `GRPC_PYTHON_BUILD_SYSTEM_OPENSSL=1` and `GRPC_PYTHON_BUILD_SYSTEM_ZLIB=1` and then try to install the dependency again.
+
 ## Contributors
 [See contributors](https://github.com/safe-global/safe-transaction-service/graphs/contributors)